The invention relates to an over-center hinge for cabinet doors, having two hinge links pivotingly joined, in the manner of a quadruple knuckle joint, at one end to a door-related hinge member and at the other end to a wall-related hinge member in the form of an elongated supporting arm, which, in the swing from the closed to the open position, can be moved through a dead center position on one side of which it is biased by the tension of a torsion coil spring toward the closed position and on the other side of which it is biased by the tension of the torsion coil spring toward the open position, one end of the torsion coil spring, disposed in the front terminal portion of the door end of the supporting arm, engaging a prolongation on the supporting arm end of one of the hinge links, which forms with the pintle at the supporting arm end of this link a lever arm which is directed away from the pintle such that, when the hinge is in the closed position, it is biased for swinging in direction closing direction, and, when the hinge is in the open position, it is biased for swinging in the opening direction.
Such over-center hinges, which are biased by spring tension towards two stable end positions, have the advantage that a door mounted on a cabinet with such a hinge will not remain in intermediate positions, i.e., it will not remain half open, so as to be damaged by drawers disposed in the interior of the cabinet, such as drawers for pots or for provisions, or fold-out slides carrying kitchen appliances, in the case of kitchen cabinets, for example. Such an over-center hinge is known from German Offenlegungsschrift No. 21 17 828 in which, asise from a V-shaped leaf spring or wire spring, a torsion coil spring for the production of the spring bias is proposed, the spring being so disposed that the spirals of the torsion coil spring are looped about the pintle on the supporting arm end of the outer hinge link farther from the supporting wall, while the free end of one of the legs of the spring engages a projection on the terminal portion of the supporting arm end of the other, i.e., inner, hinge link, while the second leg of the spring thrusts against the supporting arm. The arrangement of the spirals of the torsion coil spring on the pivot pin of the outer hinge link results in a weakening of the hinge link in the articulation area, which gives rise to doubts with regard to endurance. Furthermore, the pivot point at the supporting arm end of the outer hinge link must be concealed in the supporting arm so that the spirals of the torsion coil spring will not be visible. But then this pivot point is hard to reach. Lastly, the known design has the additional disadvantage that the torque acting in the opening direction beginning from the dead center is relatively weak, so that it more or less merely helps in the overcoming of the bearing friction, but is not capable of automatically moving the door mounted with the hinge to the fully open position and holding it there.